Step 1:

Open Outlook 2013

Step 2:

Go to the Calendar section and click Open Calendar in the Outlook Ribbon

Step 3:

Choose From Internet... in the Pop-up Menu

Step 4:

Enter the following URL in the dialog window:

https://tanzquotient.org/de/events/calendar.ics/ 

Step 5:

Click Advanced... to specify a calendar name

Step 6:

Type a name into the Folder Name box.

Press OK.

Outlook goes back to the previous Dialog. Press Yes to insert the calendar.